Air Traffic Control: How It Started and Where It's Headed

Air Traffic Control. It's the invisible mesh keeping the airways clear, the radio waves sent from ground to aircraft to organize which airplane turns in which direction at which time, the small slice of communication the keeps millions of traveling passengers safe each year. Boeing, Airbus and Embraer make the most complex flying machines known to man, but without a serving of Air Traffic Control (ATC) our airports can't make them land.

The need to organize air traffic has been around since almost the beginning of flight itself, less then twenty years after the Wright Brothers made their first faithful journey in Kitty Hawk. It all started with a guy named Archie League and a series of flag signals at the head of a runway; a red flag meant "hold" while a checkered flag cleared an aircraft for landing.

Of course, ATC has matured since then – but not as dramatically as one might think. As commercial air travel started to gain traction in the '30s, the first regimented science of directing flights began, with simple radio communication between an airport tower and an incoming aircraft. Intermediate towers kept in touch and in contact with the aircraft along certain corridors of travel. RADAR (Radio Detection and Ranging) was integrated into the process in the late 1940s and in this way, controllers could use a combination of radio communication and visual tracking to monitor exactly where each aircraft was along its flight plan. Today over 90% of the United States is covered by this technology.

(A typical day at an airport in 1948:)

Since the advent of radar for aviation, air traffic controller visualization and data processing methods have improved several fold through various technology improvements. New operational display systems, for example, have led to better data collection and manipulation for controllers – but the same primary principles have stayed in place for tracking aircraft: radar detection and radio communication.

Ironically, it's these technologies that are preventing the improvement of traffic management. Radar is limited in its ability to accurately and quickly place a moving object due to the rate at which it collects data – or because the signal to noise ratio is too low. Because of this inaccuracy, airplanes are spaced a modest distance from one another during takeoff and landing. Currently, aircraft are allowed to land with one to four minutes between each airplane, all depending on the weather, runway and aircraft.

This can cause a problem in heavy traffic regions, particularly in the New York City corridor. With so much traffic flying in and out of JFK, LaGuardia and Newark, airlines have the maximum (if not more) of flights scheduled to depart and arrive per hour out of each port. Any sort of weather, mechanical or Biblical delay causes those departures to cascade back and then landing and departure slots to get reshuffled.

If flights can't correctly get in and out of the New York corridor, subsequent flights out of hubs across the country are also impacted, and the entire country has to pay for an East Coast delay. That's why your flight from Chicago to San Diego can be delayed by an "air traffic control hold" even though both airports are clear and there's not a drop of bad weather anywhere in between.

Making the Skies Safer

To fix the congested skies, air traffic control needs to be adjusted in a big way. And that's where Global Positioning Systems (GPS) come into play. With an accuracy in feet (if not inches) and fast data turnaround, GPS has the ability to better track, report on and help organize flights for ATC purposes, and that means more flights moving through busy airports and fewer delays.

Getting the entire system up to speed is the challenge. Whereas radar can be used to actively track fleets from one fixed location, for GPS tracking to work, each aircraft needs to be equipped with a signal receiver and a transponder – that is, each airplane needs to be able to get GPS coordinates and tell other aircraft and towers its location. So rather than a marginally expensive airport retrofit, we're talking a grossly expensive fleet upgrade.

It's all done through an onboard Automatic Dependent Surveillance-Broadcast (ADS-B) system, which takes data from multiple sources, packages the signal and communicates accurate positions throughout the skies to other aicraft and to the control tower. It's a high-tech, extremely accurate system, but there's also a hefty price tag involved.

As you can imagine, the airlines, their lobbyists and special interest groups have therefore been dragging their fleet on the upgrades. But as the nation's skies become more congested and air travel picks up again, it's the only solution to effectively managing traffic.

Eventually, integration of the ADS-B tracking system into each commercial aircraft will lead to broad tighter control over air traffic across the United States, a system that the FAA calls NextGen. With luck, that system and our flights will be better streamlined by 2018. And with projections for air traffic to double in the next twenty years, we're going to need every improvement that we can get.